Recommended expert

H̊akan Källberg

Consultant

H̊akan Källberg
Ladenburg, Germany

Experience

Jan 2024 - Present
2 years 1 month
Ladenburg, Germany

Consultant

Simulina GmbH

  • Project planning of photovoltaic systems for a citizens' initiative
  • Design of billing systems
Feb 2022 - Oct 2023
1 year 9 months
Darmstadt, Germany

Consultant

Simulina GmbH

  • Migration of a distributed application to new hardware on Linux, Solaris, and AIX
  • Porting OpenSolaris tools to Linux
  • Using Universal Packet Manager and EPM for packaging across different architectures
  • Shell script programming
  • Use of GitLab
Jan 2022 - Apr 2022
4 months
Königsbach-Stein, Germany

Consultant

Simulina GmbH

  • Development of a web application for billing charging sessions in an EV charging station park
  • Management of charging stations, users, and RFID cards
  • Implementation using Python/Django on a Raspberry Pi
Sep 2021 - Dec 2021
4 months
Weiterstadt, Germany

Consultant

Simulina GmbH

  • Testing dial-in solutions in a carrier environment
  • Test automation with RobotFramework
  • Network testing with Scapy
  • Use of Git, GitLab, Debian, Jira in a Scrum environment
May 2021 - Jul 2021
3 months
Bremen, Germany

Consultant

Simulina GmbH

  • Porting from Python 2 to Python 3
  • Use of Git, GitLab, and Debian in the Scrum process
Jul 2019 - Feb 2020
8 months
Vienna, Austria

Consultant

Simulina GmbH

  • Developed a gateway for the TALQ Smart City protocol on Digi embedded computers
  • Established communication via the WirePas mesh network protocol and the REST-based TALQ protocol
  • Implemented in Python 3 with Twisted
Jan 2019 - Jun 2019
6 months
Stuttgart, Germany

Consultant

Simulina GmbH

  • Created a REST interface for data forwarding over sockets to an Unreal server
  • Planned a WebSocket interface
  • Programmed in Python
  • Used Git with Bitbucket and Jira
May 2018 - Oct 2018
6 months
Düsseldorf, Germany

Consultant

Simulina GmbH

  • Developed a QR code reader app with Python TK (tkinter)
  • Connected to the dcTrack backend system via a JSON-based REST API
  • Packaged in Python
  • Performed usage analysis of QR codes
Jan 2018 - Mar 2018
3 months
Düsseldorf, Germany

Consultant

Simulina GmbH

  • Programmed and designed APIs using Django REST framework
  • Created an API to manage nameserver data
  • Evaluated Flask, Twisted, and SQLAlchemy as alternatives
Dec 2016 - Apr 2017
5 months
Frankfurt, Germany

Consultant

Simulina GmbH

  • Connected mobile laptops with encrypted file systems
  • Installed VS-NfD systems with VPN connections
  • Set up Secunet SINA workstations and SINA smart cards
  • Developed small Python and Bash scripts
Jan 2013 - Mar 2016
3 years 3 months
Garmisch-Partenkirchen, Germany

Consultant

Simulina GmbH

  • Supported the eGap research project in Garmisch-Partenkirchen in the field of e-mobility
  • Co-developed a multi-tenant e-mobility platform as a business-as-a-service
  • Connected charging stations via LyconSys routers using OpenVPN behind firewalls and UMTS routers
  • Communicated via REST-based web services and integrated external geo services
  • Used Python, Bash, MySQL, PHP
  • Programmed charging station controllers on embedded Linux devices in Python
  • Displayed real-time charging data with Crossbar and microservices
  • Phone-based activation using SIP-Gate and Asterisk server
Sep 2012 - Dec 2012
4 months
Stuttgart, Germany

Consultant

Simulina GmbH

  • Managed email and domains with Postfix and Bind
  • Wrote scripts in Perl, Python, and Bash
  • Introduced Git as a repository
Feb 2010 - Jul 2012
2 years 6 months
Schriesheim, Germany

Consultant

Simulina GmbH

  • Collaborated on the FutureFleet research project in e-mobility
  • Developed charging management software for electric cars in Python
  • Web programming and data exchange using PHP and MySQL
  • Designed architecture with REST APIs and XML/XSD, later adding JSON interfaces
Jul 2009 - Jan 2010
7 months
Frankfurt, Germany

Consultant

Simulina GmbH

  • Software development on the LyconSys router platform (embedded Linux)
  • Shell scripting, software packaging, and web programming
May 2009 - Jun 2009
2 months
Germany

Consultant

Simulina GmbH

  • Developed in C on AIX
  • Adapted existing RADIUS tools for IPv6
Jan 2009 - Present
17 years 1 month

Consultant

Simulina GmbH

  • Creation of a membership management system for a sports club
  • Implementation of a mailing list management system in PHP/MySQL/Perl
  • Expansion into a multi-tenant solution
Jan 2008 - Present
18 years 1 month
Sweden

Consultant

Simulina GmbH

  • Setup of a call center based on Asterisk
May 2007 - Apr 2009
2 years
Germany

Consultant

Simulina GmbH

  • Testing customer-specific DHCP and RADIUS software on AIX
  • Scripting and log analysis with Perl
Mar 2007 - Present
18 years 11 months
Germany

Consultant

Simulina GmbH

  • Setup of eGroupWare with LDAP as a contact database for VoIP phones (Snom)
Jan 2007 - Feb 2007
2 months

Consultant

Simulina GmbH

  • Development of a call center agent application with LAMP
  • Perl CGI scripts for Excel export and import
Dec 2006 - Present
19 years 2 months

Consultant

Simulina GmbH

  • Built a server rack with a switch, Astaro firewall, UPS, and a Linux-based SAMBA/Intranet server
Nov 2006 - Present
19 years 3 months

Consultant

Simulina GmbH

  • Installed and commissioned an Astaro firewall with a VPN link
Oct 2006 - Present
19 years 4 months

Consultant

Simulina GmbH

  • Set up a Zarafa Outlook server on Linux/MySQL
Jan 2006 - Dec 2006
1 year

Consultant

Simulina GmbH

  • Developed multiple Asterisk-based PBX systems worldwide
Jul 2004 - Jul 2011
7 years 1 month

Consultant

Simulina GmbH

  • Implemented VoIP solutions with Cisco and Asterisk VoIP servers over ISDN-PRI
  • Integrated IP PBX systems and installed VoIP phones
Mar 2004 - Present
21 years 11 months

Consultant

Simulina GmbH

  • Preparation and delivery of a technician training on s390 Linux, zSeries
Jan 2004 - Dec 2004
1 year

Consultant

Simulina GmbH

  • Definition and implementation of firewall, VPN, and mail concepts for the public sector and SMEs
  • Installation and setup of mail systems with spam control (SPF, greylisting)
Jan 2003 - Dec 2004
2 years

Consultant

Simulina GmbH

  • Setup of various web hosting environments on Linux and Solaris platforms
Jan 2003 - Dec 2003
1 year

Consultant

Simulina GmbH

  • Webmaster role for a brokerage group
  • Creation of an automated billing system for web transactions
Jan 2002 - Present
24 years 1 month

Consultant

Simulina GmbH

  • Conceptual and security analysis at a trading company including firewall consulting and installations on Linux, Solaris, and Cisco
Jan 2002 - Dec 2002
1 year
Frankfurt, Germany

Developer

Reuters AG

  • Modification of an application for Reuters on Solaris in C/C++
  • Integration of license management and additional calculation functions
Jan 2000 - Dec 2002
3 years

Developer

Telekurs AG

  • Development of an interface for securities master data import into the SAP Treasury System
  • Use of WebMethods, Perl, and XML/DTD
Jan 1999 - Dec 2000
2 years
Frankfurt, Germany

Developer

Commerzbank AG

  • Development of a disaster recovery tool for mirroring data centers
  • Programming in Perl with Sybase database
  • Platforms: Sun E10k, Brocade SAN, EMC Symmetrix
Jan 1997 - Dec 1999
3 years

Developer

SAP/Reuters

  • Interface programming for SAP Treasury for real-time import of Reuters market data
  • Use of Solaris, C++, and Triarch SSL

Skills

  • Backend Programming
  • Software Engineering, Backend Programming/scripting
  • Rest Apis
  • Interface Programming/apis
  • Websockets Microservices
  • It Consulting
  • Consulting For Solar Power Systems And E-mobility
  • Project Management
  • Voip - Call Centers, Pbx, Asterisk
  • Security, Firewalls, Network Management
  • Mail And Web Solutions
  • Mail Server/groupware: Postfix, Egroupware, Zarafa
  • Client/server And Storage Consolidation
  • Installation And Integration
  • System Administration - Focus On Networks/linux/solaris
  • Individual Training
  • It Experience Since: 1983
  • Hardware: Sun Hardware
  • Cisco Routers And Switches
  • Lyconsys Routers
  • Operating Systems: Linux (Especially Suse)
  • Solaris
  • Development Tools: Python (Twisted, Django)
  • Microservices: Wamp/websockets, Crossbar/autobahn
  • Xml/xsd - Json
  • Perl
  • C++/c
  • Php
  • Simula 67
  • Subversion, Git, Gitlab
  • Databases: Mysql/mariadb
  • Postgresql
  • Sybase
  • Mongodb
  • Database Interfaces: Python
  • Perl/dbi
  • Sql
  • Odbc
  • Network Knowledge: Tcp/ip
  • Intranet/internet/apache
  • Ethernet
  • Firewalls - E.g. Astaro, Ip Filter
  • Snmp
  • Wlan, Vlan
  • Openvpn
  • Ipsec, Ipv6
  • Voip, Asterisk, Pbx Systems
  • Cisco Ios
  • Groupware/crm: Egroupware, Zarafa, Owncloud, Nextcloud ...
  • Sugar Crm
  • Tcp/ip-based Services (Smtp/mail - Postfix, Imap, Ftp, News, Dns, Nfs, Nis/nis+, Samba, Www/http, Ssh, Ssl, Voip, Etc.)
  • Client/server Programming
  • Shell Programming (Sh, Bash, Csh/tcsh, Ksh, Perl, Python)
  • Transaction Systems, Data Import, Export, Conversion
  • Porting And Migration Of Existing Applications To The Target Unix Platform (C/c++)
  • Storage, Raid, Lvm, Backup
  • Linux Ha
  • Customization, Extension, And Enhancement Of System-level Software
  • Computer-based Documentation Systems (Tex, Latex, Postscript, Pdf, Html, Groff, Markdown)
  • System V Packaging
  • Linux (Rpm) Packaging

Languages

German
Native
Swedish
Native
English
Advanced
Spanish
Elementary
French
Elementary

Education

Chalmers University of Technology

Physics, Computer Science · Gothenburg, Sweden

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